Expert’s Survey on 28th & 30th Oct 2013

Update from the expert’s.

Meon Valley Project Archaeological Surveys

Expert survey, 28th – 30 Oct 2013*

Introduction

Liss Archaeological Group was invited to undertake a geophysical survey on arable farmland in the Meon Valley. A large quantity of artefacts had previously been recovered by metal-detectorists in an area associated with crop marks. The nature of the finds strongly implied Romano-British activity. On the basis of this evidence the site has been deemed highly sensitive and in order to maintain its security community participation was not involved. No previous geophysical survey or excavation had taken place within the area and a recent field walk produced little evidence of activity.

Geophysical surveys

The prime objective of the survey was to look for geophysical evidence of archaeological activity, particularly in the areas where the finds were made and the cropmarks observed. Magnetometry and resistivity techniques were employed. Magnetometry detects tiny variations in the strength of the earth’s magnetic field, which can be caused by the presence of local ferrous materials, but can also be caused by the presence of accumulations of burned material. The technique is therefore useful for finding hearths and kilns. Burned items, such as burned structures, ash and accumulations of kiln-fired items, for example pottery and tile in ditches or pits can also be discovered. Resistivity detects changes in drainage characteristics of the soil caused by underlying features such as wall foundations or backfilled ditches. Overall both techniques complement each other in their ability to find areas of archaeological interest.

Method

A baseline was established, from which the survey grid was offset. The resistivity equipment was a Geoscan RM-85 resistivity meter owned by Liss Archaeological Group. The sampling interval used was 1 metre and the traverse interval was also 1 metre. The magnetometry equipment was a Geoscan FM-36 fluxgate gradiometer, loaned by English Heritage. The sampling interval used was 0.25 metre and the traverse interval was 1 metre.

Fig. 1 Anomalies showing on the Magnetometry Results

 

Fig. 2 Anomalies showing on the Resistivity Results

Results

Major magnetometry anomalies. M1. is the main feature: a sub-rectangular anomaly aligned approximately N-S, which encloses an area of 6,272 square metres. Given the nature of metal detecting finds in the area, it is probable that this is a Romano-British enclosure with quantities of kiln fired and burned materials accounting for the strength of the anomaly. The stronger signals observed along the western and north-western sections of the enclosure probably represent greater

quantities of deposited debris in these areas suggesting that human activity would have been greatest in that part of the enclosure. During the survey, a small number of pottery fragments as well as Ceramic Building Materials (CBM) were collected. One of the latter fragments can be positively identified as a ‘lipped’ section of Romano-British Tegula, which were used to roof Romano-British buildings.

M2. There is a much weaker magnetometry signal within M1 at M2 on the lower eastern edge of the enclosure; it is probably the gateway into the enclosure.

M3. Broadly parallel lines are visible to the east and west of M2 and probably represent the ditches of a trackway.

M4. Subdivides the enclosure in the north-west corner and contains in the north-west corner M6 (shaded light blue), which may represent a scatter of building debris.

M8. A very clear, linear anomaly extending from the eastern edge of the enclosure. It is possible that the feature may continue further to the east – possibly into adjoining fields on the northern side.

M12 is of interest when considered in conjunction with the resistivity anomaly R12 (discussed below).

Major resistivity anomalies. R1. The outline of the enclosure (analogous with M1).

R2. The location of the entrance to the enclosure (c.f. M2.)

R3. The ditch lines of the suggested trackway and corresponds precisely with magnetometer feature M3.

R4. Corresponds with the enclosure subdivision M4.

R6. An area of lower resistivity (white) within the north-west corner of the enclosure corresponding with M6 and could corroborate the possibility of building debris in the area.

R12. An interesting ‘lyre-shaped’ feature of higher resistance with the opening facing towards the south-south-west. Magnetometry feature M12 is a highly polarised, small feature which is located exactly in the middle of R12. R12 is therefore of interest as a possible kiln/oven.

Overall, the resistivity results fully support those derived from magnetometry.

Fig 3 Tentative combined schematic of the features discussed.

Summary

Magnetometry was particularly effective at the site and appears to have captured an entire (probably Romano-British) enclosure with an entrance in the eastern perimeter. A trackway is suggested which runs across the enclosure towards a partitioned area which may contain remains of a building. The resistivity results were affected by heavy recent rain, but are fully corroborated by the magnetometry.

Some features, such as the trackway, seem to extend into fields that were outside the scope of this survey, but it is suggested that further survey work might be considered to more fully understand the nature of the suggested trackways and also of any field systems that may be associated with the enclosure. It would also be worthwhile to return when conditions are improved to conduct a higher resolution resistivity survey over the north-western quadrant of the enclosure in the search for suggested buildings.

* This summary is based on a report of the fieldwork conducted at the site by Liss Archaeological Group (LAG)